Generally, a thick film composition comprises a functional phase that imparts appropriate electrically functional properties to the composition. The functional phase comprises electrically functional powders dispersed in an organic solvent containing a polymer. These compositions will typically contain a binder, e.g., a glass frit. Such a composition is fired to burn out the polymer and solvent and to impart the electrically functional properties. However, in the case of a polymer thick film, the polymer remains as an integral part of the composition after drying and only the solvent is removed. A processing requirement may include a heat treatment such as curing as known to those skilled in the art of polymer thick film technology.
Polymer thick film (PTF) resistor compositions are screen printable pastes which are used to form resistive elements in electronic applications. Such compositions contain resistive/or conductive filler material dispersed in polymeric resins which remain an integral part of the final composition after processing. The compositions can be processed at relatively low temperatures, namely the temperatures required to cure the resin. The actual resistivity/conductivity of the compositions will vary depending on the desired end use. PTF materials have received wide acceptance in commercial products, notably for flexible membrane switches, touch keyboards, automotive parts and telecommunications.
Many PTF compositions are only stable up to approximately 200° C. and therefore do not lend them to be used in a process subject to a temperature over 200° C.
It is therefore a primary objective of this invention to produce a PTF resistor paste composition which can be used in higher temperature process or operation conditions.